It is known to provide a valve operating mechanism for an internal combustion engine, in which the amount of lift of the valves and/or the opening and closing timing of the valves can be varied. One such apparatus is disclosed in WO 94/21897. This document discloses a system in which a first push rod is actuated by a camshaft, and causes a pivoted lever to oscillate. The lever has an upper arcuate surface, which supports a second push rod. The second push rod is connected to a rocker which causes the valve to be opened and closed. The second push rod is connected to the rocker by a ball and socket joint. The second push rod is moveable along the arcuate surface of the lever, such that its position on the lever affects the amount of lift of the valve. This arrangement alters the effective total length of the first and second push rods, to vary the amount of valve lift. This document also describes the use of a second camshaft connected to the pivot of the lever. The second camshaft has the function of varying the valve timing. This document has the disadvantage that a separate camshaft must be provided in order to vary valve timing, separate from the mechanism for altering valve lift.
Accordingly, improvement is desired in the construction of valve operating mechanism to provide a mechanism which avoids disadvantages of prior mechanisms.